The present invention relates to a foot cushioning device and more particularly relates to a foot cushioning device which has associated shock absorbing structure to absorb and relieve shock imposed on the foot, particularly in the heel area.
Running for health and fitness has increased in popularity in the last ten years. Persons of all ages run both recreationally, for fitness and in competition at different levels. With the increased emphasis on competitive running, runners and joggers have had to increase the intensity of their training by running greater distances. Serious competitive runners preparing for an event such as a marathon commonly run as many as seventy miles a week or more. Even those who run for recreation and fitness may run substantial distances each week. Accompanying this increased activity is a greater risk of injuries due to over use. Many of these are degenerative disorders which occur in the lower extremities due to the shock imposed on the body.
It has been estimated that as many as forty million Americans participate in some form of running. Statistics indicate that 50% to 70% of these individuals will suffer from some type of running-related injury. For example, running twenty miles a week for a period of thirty years will result in the body being subjected as many as fifty million shock waves.
Shock waves are due to external forces. Some of them are produced by constraints such as the running surface, sport equipment. In walking, running, jogging or jumping, the ground reaction force is the most important external force. The magnitude of the ground reaction force, its direction and point of application have an influence on the loads imposed on the body. Ground reaction force, both magnitude and direction and point of application depend upon a number of factors. Various devices can be found in the prior art to absorb the impact and shock forces imposed on the foot, particularly the heel. Generally these devices are orthopedic devices which serve to alleviate conditions such as shock and serve to maintain the heel and the foot in the proper anatomical attitude to prevent the tendency of the foot to pronate. Some running shoes incorporate shock absorbers and also provide stability of motion control for the runner. To satisfy these requirements, some compromise generally has to be made by the shoe manufacturer. Thus, it becomes increasingly important to supplement the built-in shock absorbing capacity of the footwear with additional shock absorbing capacity which can be provided by a specially built heel cup or similar device.
One such auxiliary shock absorbing device which is intended to be inserted in some type of footwear is shown in my prior patent, U.S. Pat. No. 4,619,055. This patent discloses a cushioning pad or mat which is insertable in footwear having an upper laminae of material having moisture absorbing characteristics with an intermediate laminae and a lower cushioning pad. When used as an insole, the device is provided with various sizes and shapes for insertion in shoes. Air holes are provided at spaced intervals and a special cellular design provides a bellows action to enhance flow of air around and through the insole and also serves to improve blood circulation to the extremities of the user.
Another foot cushioning device is also shown in my prior patent, U.S. Pat. No. 4,179,826. This device which has achieved considerable success is sold under the trademark TULI'S and has a body defining a cup-like recess to receive at least the heel or os calcis portion of the foot. The device is insertable in ordinary footwear. The exterior of the heel cup body is provided with shock absorbing projections extending from at least the rear of the heel portion at the underside of the foot. The projections deform and deflect to protect the foot by absorbing shock forces on the weight-bearing portions of the foot.
U.S. Pat. No. 4,974,343 shows a unique foot cushioning device which has a heel cup to fit over the heel of the wearer which is attached to an elastic anklet. The anklet is preferably constructed of an expandable elastic material and serves to support the ankle area of the user and to secure the shock absorbing heel cup in the proper position. The device provides a complete foot appliance which controls the pronation and supination of the heel and stabilizes the ankle.
While, as indicated above, the aforementioned devices are representative of the prior art and have achieved considerable commercial success and are of significant help to many users, there nevertheless exists a need in many instances for an improved shock absorber which effectively simulates the biomechanical behavior of the human heel pad.
The present invention provides a novel and unique foot cushioning device which in a preferred embodiment includes a heel cup portion designed to fit over at least a portion of the heel of the wearer in the area of the os calcis. The exterior of the cushioning device beneath the heel bone is provided with projecting shock absorbing members. The shock absorbing members are configured to simulate the physiological behavior of the human heel pad and in the preferred embodiment are configured as a plurality of interconnecting longitudinal and transverse ribs of varying height. When the taller ribs begin to collapse there is relatively low resistance deformation. With the increase in global deformation, the taller ribs collapse the length of the shorter ones and at this point both the taller and shorter ribs provide resistance to load resulting in a non-linear force displacement behavior similar to that which occurs with the human heel pad. The shock absorbing members may be also provided in other various configurations such as cylindrical projections of varying length. In the preferred embodiment, the device is adapted to be worn in the shoe and the shock absorber arranged on a cup-shaped body. The medial and lateral sides of the cup conform to the appliance to the heel seat of a shoe so the device can be conveniently inserted in a conventional shoe. The device is formed and preferably molded from any relatively soft flexible material such as natural or synthetic rubber or other suitable thermoplastic material.
In other embodiments, the device may be formed simply as a generally planar insole or the design can be incorporated into the heel or insole portion of an athletic shoe.
The above and other objects and advantages of the present invention will become more apparent from the following specification, claims and drawings in which: